do you put a comma before and in a list

In most cases, it is customary to put a comma before "and" in a list of three or more items. This is known as the Oxford comma or serial comma.

For example:

• "I bought apples, oranges, and bananas."

In this sentence, the comma before "and" is the Oxford comma. However, the use of the Oxford comma is a matter of style, and there are some cases where it may not be necessary or appropriate to use it.

It's worth noting that different style guides have different recommendations regarding the use of the Oxford comma. For instance, some style guides, such as the Associated Press (AP) style guide, do not use the Oxford comma, while others, such as the Chicago Manual of Style, do recommend its use. If you are writing for a specific publication or organization, it's a good idea to check their style guide to see what their recommendations are.